Moving a vehicle from rest in highway conditions is well understood. Generally speaking the vehicle transmission is provided with a device to manage the transition of a driven element from a stationary condition to a condition of rotation at engine speed; the device is typically a friction clutch. Slippage of the vehicle tyres on the highway surface is considered negligible, and in any event is undesirable since it may cause excess tyre wear and instability of the vehicle; vehicle drivers are taught to avoid spinning the vehicle wheels, and this is not difficult on a highway where friction between the tyres and the surface is relatively consistent. Maintaining progress once the vehicle is in motion is assured because of the high friction co-efficient between tyres and road.
Where friction between the vehicle tyres and the ground surface is reduced or inconsistent, a conventional approach to drive away may result in relative slipping. This is particularly problematic for novice drivers in off-highway conditions. For example on sand, injudicious spinning of the wheels may cause the vehicle to dig a hole and become stuck. The novice off-highway driver may not appreciate, from inside the vehicle, that wheels are spinning, and the fitment of deep tread off-highway tyres may exacerbate this problem due to their tooth-like excavating properties.
Furthermore, when the vehicle is in motion, it may be relatively easy to spin one or more wheels and thereby lose traction, especially if the friction co-efficient between the tyres and ground surface is inconsistent.
It is against this background that the present invention has been conceived. Embodiments of the invention may provide a method and system of moving a vehicle from rest and of maintaining progress, which is adapted to unknown terrain, which will enable effective transition of the vehicle from a stationary to a moving condition, and which will allow progress to be maintained. Other aims and advantages of the invention will become apparent from the following description, claims and drawings.